1. Field of the Invention
The invention relates to a cylinder lock mountable on a door panel to control a latch, more particularly to a cylinder lock having improved mechanical strengths to bear against high torsional, compression and tensile stresses.
2. Description of the Related Art
A cylinder lock typically includes a drive mechanism that can be operated through an inner or outer handle so as to retract a door latch to an unlatching position. The drive mechanism generally includes inner and outer drive spindles connected respectively to the inner and outer handles, and a latch retractor connected to the inner and outer drive spindles and coupled to the door latch. When the inner or outer handle is rotated, the rotational movement thereof is transmitted to the inner or outer drive spindle, and the latch retractor moves the door latch to the unlatching position. However, the inner and outer drive spindles are prone to damage when a torque is applied improperly or excessively to the inner or outer handle.
U.S. Pat. No. 6,893,059 discloses a cylinder lock that has two axially extending mounting rods to reinforce torsional strength of a drive mechanism. Each of the mounting rods has two ends fixed to inner and outer rose liners of the cylinder lock, and is embedded partially and axially in an outer shell of the drive mechanism so that a portion of each mounting rod protrudes from the outer shell of the drive mechanism. To assemble the drive mechanism in a door panel, in addition to a cylindrical lock hole formed in the door panel to receive the drive mechanism, positioning grooves are provided in the door panel at two diametrically opposed positions of the cylindrical lock hole for receiving partially the mounting rods. As the outer shell of the drive mechanism is coupled rigidly to the inner and outer rose liners through the mounting rods, the outer shell of the drive mechanism has an increased torsional strength to bear the torque applied to the drive mechanism. However, the mounting rods are insufficient to strengthen interior component parts of the drive mechanism, such as a latch retractor housing, disposed within the outer shell.